void main() {
    Scanner sc = new Scanner(System.in);
    System.out.println("请输入一个字母");
    String letter = sc.next();
    switch(letter) {
        case "a":
        case "e":
        case "i":
        case "o":
        case "u":
            System.out.println(letter + "是元音字母");
            break;
        default:
            System.out.println(letter + "不是元音字母");
            break;
    }
}
